A surf and turf is a term used to describe a dish you can order that usually has some land dwelling animal such as beef, and a fish accompaniment. When used for fun and as slang it refers to the game some men play, where you go out hogging or whaling, both are terms for larger women. When you are able to make love to both types of larger women in the same night you have just enjoyed a Surf N' Turf.

When a straight couple is having sexual intercourse in the missionary position while another man and/or woman licks both of their sexual organs at the same time

Jared: Last night was fucking crazy man!
Steve: Why bro?
Jared: Cuz I was pounding your sisters taco with my man hammer and your girlfriend came in and started licking my bitches pussy and my dick at the same time!
Steve: aw, the old Surf N Turf?